Selective Calling

The other set of DPDT relay contacts are used to control connecting audio-in to audio-out. This Audio Switching may be used to remotely turn a speaker on and off for Selective Calling or other applications.

4 Separate DTMF Access Codes

Each access code uses from 1 to 10 DTMF digits to provide 4 unique DTMF combinations for controlling the relay.

UnMute Switch

A front-panel slide switch provides a Selective Calling Override or UnMute function when moved to the left position. In this position, audio in is always connected to audio out for monitoring the radio receiver, tape recorder, or other audio source. Nevertheless, when a valid DTMF relay command is received, the relay dry contacts are switched normally, performing their designated function. When the UnMute Switch is slid to the right, Selective Calling is enabled, and audio in is only connected to audio out when the relay is activated.

Green LED

The green front-panel LED serves two functions in the AK-1C. It's default usage is as a power-on indicator. It will blink off as each valid DTMF character is received. When programming the AK-1C configuration parameters, the LED is turned off, and blinks on to indicate receiving DTMF characters.

Yellow LED

The yellow front-panel LED is on when the relay is on, and off when the relay is off.

Red LED Call Alert

When the relay is activated, either latched on or momentarily pulsed on, then off, the red LED is flashed continuously to provide a call alert. Toggling the UnMute slide switch cancels the call alert, returning the LED to normal operation.

Long Tone Zero

The AK-1C also supports LiTZ compatible signaling. This protocol is often used in Amateur Radio for emergency calls. The minimum duration required for a DTMF zero to be considered a valid Long Tone Zero may be set to from 1 to 9 seconds.

Relay Pulse

Time When an Access Command is decoded, the pre-configured relay action is taken: Latch, Unlatch, or Momentary. The duration of a momentary pulse is determined by the pulse parameter value set up during configuration of the AK-1C. Pulse durations of: 1, 5, 10, 30, or 60 seconds, or 3, 10, 30, or 60 minutes are selected according to the configuration value used as shown in this table:

value 1

value 2

value 3

value 4

value 5

value 6

value 7

value 8

value 9

1 sec

5 secs

10 secs

30 secs

60 secs

3 min

10 mins

30 mins

60 mins

Programming The AK-1C

EEPROM parameters are configured by connecting a DTMF source to the 3.5mm audio-in jack and
then pressing the on-board program pushbutton. Then up to 4 separate Access Commands may be entered thus:

Press program button to enter programming (LED goes out, blinks for each DTMF character entered).

Enter the command number: 1-4

Enter the relay action character:

* = relay latch; # = relay unlatch;

1-9 = relay momentary time (see above);

0 = Disables selected access code

Enter the 1-10 DTMF character Access Command sequence which will trigger the relay action.

Press program button to exit (status LED comes back on solid.)

In addition to general use relay commands 1-4, the AK-1C supports Long Tone Zero relay actions using command 5. It is
programmed using these steps:

Press program button to enter programming.

Enter command number: 5.

Enter the relay action character (same as above).

Enter the minimum number of seconds 1-9 for a valid Long Tone Zero.

Press program button to exit.

Group & All-Call Alerting

When multiple AK-1C units are set up to respond to the same sequence of DTMF digits or Access
Commands, they form a calling group: That is, all AK-1C units receiving that same DTMF character sequence will perform their
own configured relay action. Each AK-1C may be set to respond to one-or-more individual Access Commands, to one-or-more
group Access Commands, and/or one-or-more All-Call Access Commands.

Specifications

The AK-1B is an assembled and tested printed circuit board drawing less than 15ma with the relay coil unlatched.
Current draw is less than 30ma with the relay energized. Power is supplied by a 12 Volt DC power supply through the center-positive DC Jack. Audio input and audio output are through 3.5mm phone jacks. The AK-1C is as above, but
ships complete with Enclosure, Power Supply, and Cables.